1. Field of the Invention
The present invention relates generally to processing sheet material and, more particularly, to a sheet folding apparatus using two fold rollers that are biased away from another and an adjusting member to alter the distance between the fold rollers.
2. Background Information
Several systems for folding material are known in the art where the characteristics of particular folding components are adjustable. For instance, self-adjusting components are included in the system described in U.S. Pat. No. 5,738,620 (Ebner et al.), the disclosure of which is hereby incorporated in its entirety. In the Ebner patent, a stack of sheets is pushed between a pair of pre-folding rollers and a pair of folding rollers by a folding knife. One half of each roller pair is spring-loaded towards and pivots away from the other half when a stack of sheets is introduced by the folding knife. While such a system allows for some automatic adjustment, much force is needed to force a stack of sheets (i.e., made up of more than one sheet) between the rollers. Also, the Ebner patent may not be able to produce sharply defined folds, as the roller pairs may not be equipped with enough spring force to do so.
A system for finishing printed sheets into booklets is described in PCT Document No. WO 00/18583 (Trovinger et al.). The Trovinger PCT includes an operation where individual booklet sheets are folded using two drive motor assemblies. A first vertical drive motor assembly operates to immobilize a sheet by pressing it against a fold blade with a folder assembly. This first vertical drive motor assembly moves a set of fold rollers into contact with both the sheet and a longitudinal fold blade. The axes of rotation for the fold rollers are perpendicular to the fold blade used to fold each sheet. A second horizontal drive motor then operates to deform the sheet against the fold blade by reciprocating the set of fold rollers, which have been placed into contact with the sheet, back and forth along the fold blade to in effect crease the sheet. The number and spacing of these rollers are such that during horizontal movement of the fold rollers, at least one fold roller passes over every point along the portion of a sheet where a fold is to be formed.
The Trovinger PCT also describes the use of self-adjusting, v-shaped fold rollers, each of which include two complementary disks that are spring-loaded towards each other on a common axle. However, rollers of this configuration may not be able to produce a sharply defined fold, as described above with respect to the Ebner patent.
It would be desirable to provide for precise folding of a wide range of sheet materials where a distance between fold rollers can be easily selected and rigidly fixed.
Accordingly, the present invention is directed to an apparatus that folds sheet material by adjusting a distance between two fold rollers biased away from each other with an adjusting member and by positioning a fold blade between the fold rollers. In this way, variable media thickness can be accommodated while producing sharp folds.
According to one embodiment of the present invention, a system for folding sheet material is provided, including a fold blade, two fold rollers biased away from each other, an adjusting member which alters a distance between the two fold rollers, and first drive means for moving at least one of the fold blade and the two fold rollers along a first path to position the fold blade between the two fold rollers.
According to another embodiment of the present invention, a method for folding a sheet of material is provided, including the steps of feeding a sheet material into an area between two fold rollers and a fold blade, adjusting a distance between the two fold rollers, wherein the two fold rollers are biased away from each other, and moving the two fold rollers and the fold blade relative to one another to form a fold in the sheet using the fold blade.